Use of fossil fuel increased the concentration of acidic gas such as carbon dioxide (CO2), methane (CH4), hydrogen sulfide (H2S), carbonyl sulfide (COS) or the like in the atmosphere, which in turn resulted in global warming. In particular, various ways to reduce carbon dioxide in the atmosphere have been vigorously discussed worldwide since the Rio Summit in 1992.
Carbon Dioxide Capture& Storage (CCS) technology is a technique of separating, from the atmosphere, carbon dioxide discharged from power plants, steel factories, cement factories or the like that use fossil fuel and discharge a large amount of carbon dioxide.
Among the CCS technology, carbon dioxide capture technology is a core technology which takes up about 70% to 80% of total costs and includes a post-combustion technology, a pre-combustion technology, and an oxy-fuel combustion technology (Carbon Dioxide Capture& Storage Technology, Sangdo PARK, Physics and High End technology, June, 2009).
The post-combustion technology relates to removing CO2 generated due to combustion of fossil fuel by allowing the CO2 to be absorbed into or to react with various solvents. According to the pre-combustion technology, CO2 is separated before combustion; that is, CO2 is preprocessed by gasifying fossil fuel such as coal and converted into CO2 and hydrogen (H2), and then the CO2 is separated from the mixture gas of CO2 and H2 or the mixture gas is burned so as to capture the CO2 among the exhaust gas. According to the oxy-fuel combustion technology, instead of the air, only hydrogen is used in combustion of fossil fuel to thereby facilitate capturing of CO2. Among the above-described technologies, the post-combustion technology is currently most widely used.
The post-combustion technology is the simplest way to apply to conventional sources of carbon dioxide. The technique relates to separating carbon dioxide through adsorption and desorption of carbon dioxide by using an absorbent, and is focused on improving performance of the absorbent and improving processes according to the improved performance of the absorbent. Examples of the technique that are commercialized and operated, and used to supply carbon dioxide required for the manufacture of urea fertilizer, for automobile welding, or for carbonated drinks are a wet absorption technique and a dry adsorption technique, and the wet absorption technique has a relatively high efficiency.
A main process of the wet absorption technique is a capturing process that uses an amine absorbent. The capturing process has technical reliability in that the process has been applied to a reforming process of a petrochemical process. However, for the process to be applied to flue gas containing various pollutants, performance of the absorbent and the process are to be improved. The process in which an amine absorbent is used is a chemical absorption process in which alkanolamine, which is a combination of an alkyl group with amine and hydroxyl, is used as an absorbent, and includes an absorption tower that selectively absorbs carbon dioxide from an influx gas, a regeneration tower (heating regeneration tower) regenerating the absorbent that has absorbed carbon dioxide, and other equipment.
MEA (Mono Ethanol Amine) which is most widely used as an amine absorbent provides the cause of acid-base neutralization reaction between an alkali property formed due to noncovalent electrons of an amine group, and carbon dioxide, which is acidic, in an aqueous solution, and the generated salt (carbamate or bicarbonate) is dissolved at about 110° C. to about 130° C. to be regenerated. Amines used as an absorbent exhibit many differences in terms of absorption power and speed depending on structural properties thereof.
While a process of absorbing carbon dioxide is performed at about 40° C. to about 50° C., a regeneration process is performed at about 110° C. to about 130° C., and thus, a portion of an absorbent is gasified during the regeneration process and is discharged with carbon dioxide. Thus, a cooler to cool and condense the portion of the absorbent and a preheating technique to lower a heat duty of a reboiler of the regeneration process are required.
Korean Patent Registration No. 0983677 discloses a system and method of absorbing and separating acidic gas, in detail, a method of using steam generated in a steam-generating boiler, as a heat source for regenerating an absorbent. However, this method has limitations in that steam is used only in regenerating the absorbent.
Thus, as a large amount of energy is consumed due to heating and cooling for the regeneration process, development of technology to reduce energy consumption is required.